But:
What´s the size and range?
Have you calculated the expected accuracy? (Steps, angular resolution, etc.).
How do you do joint bearing and tensioning?
Arm droop is estimated?
How do you tension the belts?
What belts are you using? HTD ?
Where are the limit/position switches or encoders etc.?

Yeah,
Although internals and bearing contact areas are not visible, art of bearing seems to be promising.
I think GT2 is comparable with HTD, so no slip which is good.

The only thing to mention is still belt tensioning and reduction ratio (as cozmicray already meant, it will be fast but not THAT accurate,... OK acceleration might also not be perfect due to low torque). But you can calculate it.
What about an excentric belt tensioning idler, which sits inside the main arm? By Fixing it in a slightly excentrically rotated position, it presses the belt towards the outside...So you can use continuous circle belts.

Hi! A we so me idea man, I want to build one since I was a kid. What about making gears with more teeth? It will improve accuracy and reduce accumulative errors. Are the accumulative errors always the same? I mean: if we can make a scientific rule that aproximates to the value, the printer would be super accurate and fast. Looking forwards to see videos and more pics
Cheers!

How does marlin scara do the homing with the endstops and/or how can I test without homing? Now I don`t have control over the machine. I tried a lot things with endstops and changing some settings.
despite the explanation in the blog, it`s still hopeless.

Can some one give me some advice or help with the idea of endstops and marlin?